An autonomous underwater vehicle (AUV) is a robot that can operate in underwater and unstructured environments without continuous human guidance. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles (UUVs) (alternatively referred to as unmanned undersea vehicles), a classification that includes non-autonomous remotely operated underwater vehicles (ROVs)—controlled and powered from the surface by an operator/pilot via an umbilical or using remote control.
AUVs can rely on a number of propulsion techniques, but propeller based thrusters or Kort nozzles are the most common by far. These thrusters are usually powered by electric motors and sometimes rely on a bore or lip seals in order to protect the motor internals from electric shorting and corrosion. An alternative to propeller-based propulsion includes underwater gliding. An underwater glider is a type of AUV that do not directly propel themselves. They use small changes in buoyancy in conjunction with wings to convert vertical motion to horizontal, and thereby propel themself forward with a sawtooth-like up-and-down profile through the water. Because of their low speed and low power electronics, the energy required to cycle trim states is far less than for regular AUVs. In this manner, gliders trade speed and responsiveness for endurance and gain a significant increase in range and duration of operation compared to vehicles propelled by electric motor-driven propellers. However, no current AUV is capable of all aspects; speed, maneuverability, and endurance.
Existing UUVs are commonly cylindrical and exhibit poor maneuverability, particularly in littoral and riverine areas. They often use rigid bodies combined with propellers and as a result can be limited in efficiency (of propulsion and maneuvering) by the practical propeller diameter, exhibit poor transiency response, and low propulsion efficiency over ranges of speeds and maneuvers. A lack of control authority caused by a single propeller based system with a rigid body can prevent the execution of missions in cluttered and complex environments.